Data centers housing significant numbers of interconnected computing systems have become commonplace, such as private data centers that are operated by and on behalf of a single organization, and public data centers that are operated by entities as businesses to provide computing resources to customers. Some public data center operators may provide network access, power, and secure installation facilities for hardware owned by various customers, while other public data center operators provide full service software and hardware facilities that may also include hardware resources made available for use by their customers.
The advent of virtualization technologies for commodity hardware has provided benefits with respect to managing large-scale computing resources for many customers with diverse needs, allowing various computing resources to be efficiently and securely shared by multiple customers. For example, virtualization technologies may allow a single physical computing machine to be shared among multiple users by providing each user with one or more virtual machines hosted by the single physical computing machine, with each virtual machine being a software simulation acting as a distinct logical computing system that provides users with the illusion that they are the sole operators and administrators of a given hardware computing resource, while also providing application isolation and security among the various virtual machines.
A virtualized computing resource provider may sell usage of computing resources in a public data center to customers by leveraging virtualization technology. Some virtualized computing resource providers may allow customers to reserve or purchase access to resources in any of several different resource purchasing configurations. For example, a customer may reserve a virtual computing instance for a relatively long duration, such as one year or three years, or a customer may purchase resources for shorter terms on an ad-hoc basis as needed. For some types of resource reservations, at least a portion of the price paid by the customer may fluctuate over time in response to changing demand and supply of the resources within the data center.